Dong W, Warshawsky H
Department of Anatomy and Cell Biology, McGill University, Montreal, Quebec, Canada.
Adv Dent Res. 1996 Nov;10(2):232-7. doi: 10.1177/08959374960100021901.
Since high-resolution transmission electron microscopy (HRTEM) provides information on a nearly atomic level, the confidence level with this method is very high. Thus, when lattice fringe continuity is found between two enamel crystals in proximity, such continuity has been taken as evidence of crystal fusion (Daculsi and Kerebel, 1977). Similarly, selected-area dark-field (SADF) electron microscopic imaging has been used to study the axial and spatial orientation of crystals. These studies have shown that there is apparent continuity between enamel and dentin crystals (Arsenault and Robinson, 1989). This observation supported the hypothesis that enamel crystallites are initiated by crystallites in dentin. We have used both HRTEM and SADF methods to identify instances of spatial relationship between crystallites in sections of rat incisor enamel and shark enameloid. In each instance of apparent continuity, goniometric tilting was used to examine the continuous interface. All instances where two crystallites seemed to come into contact, and where HRTEM imaging showed the lattice fringes to be directly continuous, were separated into individual crystallites when the specimen was tilted a few degrees. Thus, adjacent crystallites can show lattice fringe continuity in the absence of real crystallite contact. When instances of overlapping crystallites were examined by SADF imaging, the overlapping crystallites gave a single bright image. Goniometric tilting revealed separate crystallites. Thus, neither lattice fringe continuity nor image continuity under SADF can be used as evidence of crystal continuity unless goniometric rotation and tilting are applied when spatial relationships are suspected.
由于高分辨率透射电子显微镜（HRTEM）能在近乎原子水平上提供信息，所以这种方法的置信度非常高。因此，当在相邻的两个牙釉质晶体之间发现晶格条纹连续性时，这种连续性就被视为晶体融合的证据（达库尔西和凯雷贝尔，1977年）。同样，选区暗场（SADF）电子显微镜成像已被用于研究晶体的轴向和空间取向。这些研究表明，牙釉质和牙本质晶体之间存在明显的连续性（阿尔塞纳ault和罗宾逊，1989年）。这一观察结果支持了牙釉质微晶由牙本质中的微晶引发的假说。我们使用HRTEM和SADF方法来确定大鼠切牙牙釉质切片和鲨鱼釉质中微晶之间的空间关系实例。在每一个明显连续性的实例中，使用测角倾斜来检查连续界面。当标本倾斜几度时，所有两个微晶似乎接触且HRTEM成像显示晶格条纹直接连续的实例，都被分离成了单个微晶。因此，相邻微晶在没有真正微晶接触的情况下也可以显示晶格条纹连续性。当通过SADF成像检查微晶重叠的实例时，重叠的微晶给出一个单一的明亮图像。测角倾斜显示出是单独的微晶。因此，除非在怀疑空间关系时应用测角旋转和倾斜，否则SADF下的晶格条纹连续性和图像连续性都不能用作晶体连续性的证据。
